1. Field of the Invention
The present invention relates to a flying height measurement method and system, and more particularly, to a flying height measurement method and system which can measure the flying height of a hard disk drive head slider.
2. Description of the Related Art
In general, a hard disk is rotatably installed on a base inside a hard disk drive. The hard disk drive includes at least one magnetic head that corresponds to a recording/reproduction surface of a rotating hard disk, to write or read information by magnetizing or detecting a magnetic field of the hard disk surface.
The magnetic head is installed on an arm at an end of a magnetic head assembly that is installed on the base in the hard disk drive. The magnetic head is capable of pivoting and moving to an appropriate position on the hard disk under the guidance of the magnetic head assembly.
The magnetic head assembly includes an actuator arm rotatably coupled to a pivot shaft, and a suspension coupled to the actuator arm. At the end of the actuator arm is a magnetic head slider on which a magnetic head capable of recording and reproducing information with respect to the hard disk is attached.
The magnetic head slider is biased toward the hard disk by the suspension. When the hard disk begins to rotate, the magnetic head slider flies above the disk surface due to aerodynamic pressure generated by the rotation of the hard disk. When the magnetic head slider is in a floated state, a gap between the magnetic head provided on the magnetic head slider and the hard disk surface is referred to as the flying height (FH). The flying height is designed by a computer simulation.
Recently, to increase the capacity of a hard disk, the number of tracks per inch (TPI) is increased while the width of the track is decreased. To reduce the width of the track of a hard disk, the width of the write head of the magnetic head which inputs a magnetic signal to the hard disk needs to be reduced accordingly. Also, the flying height of the magnetic head needs to be lowered to read a magnetic field written on a track having a relatively small size by using a read head.
As described above, as hard disks increase storage capacity, one of the factors that is affected by an increase of the surface recording density of a hard disk is the flying height. Thus, accurately measuring the flying height is very important to reliable operation of a hard disk drive.
A conventional flying height measurement apparatus is used by which a flying height is calculated by illuminating light emitted from a light source to a magnetic head slider flying above a glass disk, through a glass disk, and measuring the strength of light reflected by the magnetic head slider. A single light source or a multi-light source to reduce a measurement error by the single light source can be used as the light source. The glass disk can transmit light.
The flying height can be calculated by measuring the intensity of the interference light by comparing the light reflected by the surface of the glass disk and the light reflected by the magnetic head slider.
However, the flying height is affected by the degree of roughness of the surface of a disk in use, the substance of the disk, and its mechanical features. Accordingly, because the glass disk used in the flying height measurement apparatus is different from a hard disk, the flying height of the magnetic head with respect to the hard disk cannot be properly obtained by the above flying height measurement method.
Also, since the flying height is designed to be very low because of the high capacity of the hard disk, the above flying height measurement apparatus using light approximates to a limit in the measurement. This is because the flying height is too low so that a resolution power is limited due to the wavelength of light used in the measurement method. Thus, when the flying height is designed lower, a problem may be generated in the reliability of a measured value in the above measurement method using light and the measurement of the flying height designed by a simulation has a limit.